Hyalith glass

Hyalith names two historical varieties of opaque glass, one black and one red. The Corning Museum of Glass associates their development with the Bohemian glassmaker Jiří von Buquoy. It gives patent dates of 1817 for black and 1819 for red. These are patent dates, not dates for every surviving object.

Colour and a dense, opaque appearance matter when examining possible hyalith. However, not every black or red glass object is hyalith. A trade name must not replace a description of the actual material.

Record colour, form, surface, decoration and legible markings. Check whether an apparently black object transmits light through thin areas. Comparison with a documented museum object can support assessment but cannot alone establish maker, age or manufacturing location. State uncertainty clearly when attribution rests on limited evidence.

Sources: Corning Museum of Glass: Hyalith.